This invention concerns gasoline additives which are a combination of a diamine Mannich Base and a polyamine Mannich Base.
The operation of modern internal combustion engines is often made difficult by the accumulation of deposits in critical areas of the fuel intake system. Use of one type of gasoline additive to overcome a particular problem of deposit accumulation may cause certain other difficulties. For instance, carburetor detergents which are usually polar compounds such as amines, amides, amine phosphates, imidazolines and succinimides, may cause an increase in intake valve deposits. Intake valve deposit control additives are usually non-polar or low-polar materials such as top cylinder oil and low viscosity hydrocarbon polymers.
Carburetor detergents are believed to function by washing away deposits when liquid gasoline being discharged from the accelerator pump or high speed jet flows past the throttle plate. In a carburetor, such washing away of deposits takes place at relatively low temperatures. In contrast, in the vicinity of the intake valves, the temperature is in the range of 500.degree. to 600.degree. F. and the liquid gasoline which participates in the washing operation in the carburetor is largely vaporized by the time it reaches the intake valves.
Concern in controlling motor vehicle exhaust emissions has led to many engine modifications, and to the use of various emission control devices. One proposed solution for minimizing carbon monoxide emissions without engine stalling is to effect better fuel evaporation by the time the choke is off. This is accomplished by having fuel droplets from the carburetor impinge upon a plate heated by hot exhaust gases. The plate is designed to hold the fuel droplets until evaporation takes place. However, one difficulty with such a system, also called Early Fuel Evaporation (EFE) is that the high boiling ends of the fuel remaining in contact with the hot surface tend to decompose and from deposits. As the deposit accumulation increases, the plate becomes ineffective in vaporizing fuel and thus engine stalling may occur during engine warm-up.
Condensation products of an alkylphenol, an aldehyde, and an amine have been found to be effective carburetor detergents in gasoline. These condensation products are often called Mannich Bases since the reaction by which they are prepared is known as the Mannich reaction. When the amine reactant is a polyalkylenepolyamine and the aldehyde reactant is formaldehyde, the condensation product is a polyamine containing alkyl- and hydroxy-substituted benzyl substituents. Unfortunately, Mannich Bases when used in amounts sufficient to provide carburetor detergency, also cause increased intake valve deposits.
It is an object of this invention, therefore, to provide a multifunctional gasoline additive which is a carburetor detergent and which at the same time minimizes intake valve deposits and quick-heat intake manifold deposits.